Latest research in football - week 32 - 2013

Latest research in football

As previous literature updates, we have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.
Following studies were retrieved for this week:

#1 The acute effects of combined static and dynamic stretch protocols on fitness performances in soccer players
Authors: Amiri-Khorasani M, Sotoodeh V.
Reference: J Sports Med Phys Fitness. 2013 Oct;53(5):559-65.
Summary: The purpose of this study was to compare the acute effects of different stretching methods on acceleration, speed, agility, power, and flexibility in different soccer positions. Methods and results: Therefore, 16 soccer players conducted 10 m, 20 m, shuttle run agility, vertical jump, and V-sit flexibility after static (SS), dynamic (DS), combined (static + dynamic) (CS), and no stretching (NS). Relative to the no-stretching condition, there were significant differences in fitness performances after (1) DS vs. SS, (2) DS vs. CS, and (3) CS vs. SS in defenders, midfielders, strikers, and also in all players (P<0.05). Conclusion: In conclusion, it may be desirable for soccer players to perform DS during warm up prior to the performance of activities that require a high power output.

#2 Movement analysis of Australian National league soccer players using global positioning system technology
Authors:  Wehbe GM, Hartwig TB, Duncan CS.
Reference: J Strength Cond Res. 2013 Jul 26. [Epub ahead of print]
Summary: Player activity profiles of match play provide valuable information for optimal athlete training prescriptions, competition strategies and managing load and recovery and are currently lacking in elite Australian-league (A-League) soccer. The aims of the study were therefore, to (a) determine match activity profiles for elite A-League soccer players and make match-half and positional comparisons, and (b) examine the effect of situational factors including evolving match status (drawing, winning, or losing) and goals being scored and conceded on selected match activity profile variables. Global positioning system tracking devices were used to determine activity profiles of 19 elite male adult soccer players during eight pre-season matches (n = 95 files). Total distance, average speed, high-intensity-running (HIR) distance, and very high-intensity running (VHIR) distance decreased from the first to the second half by 7.92%, 9.47%, 10.10%, and 10.99%, respectively. Midfielders covered 11.69% more total distance, 28.08% more HIR distance, and had a 10.93% higher average speed than defenders (p < 0.05; d = 1.90, 1.03, and 1.83, respectively). Attackers performed 27.50% and 30.24% less medium accelerations than defenders and midfielders, respectively (p < 0.01; d = 1.54, and 1.73). Whilst the team was winning, average speed was 4.17% lower than when the team was drawing (p < 0.05, d = 0.32). Scoring or conceding goals did not appear to affect HIR. This study adds to limited knowledge of match demands in elite A-League soccer. The match activity profiles provide descriptive benchmarks that could be used to make comparisons with other elite level soccer populations while also providing a framework for game-specific training prescription, competition strategy and load management. The generalization that defenders experience a relatively lower match load may be questionable given their relatively high acceleration and deceleration demands.

#3 Single nucleotide polymorphisms associated with non-contact soft tissue injuries in elite professional soccer players: influence on degree of injury and recovery time
Authors: Pruna R, Artells R, Ribas J, Montoro B, Cos F, Muñoz C, Rodas G, Maffulli N.
Reference: BMC Musculoskelet Disord. 2013 Jul 26;14:221. doi: 10.1186/1471-2474-14-221.
Summary: The biological mechanisms involved in non-contact musculoskeletal soft tissue injuries (NCMSTI) are poorly understood. Genetic risk factors may be associated with susceptibility to injuries, and may exert marked influence on recovery times. Data on type and degree of injury and recovery time were collected in 73 male professional soccer players (43 White, 11 Black Africans and 19 Hispanics) who suffered total of 242 injuries (203 muscle, 24 ligament, and 15 tendon injuries). One single nucleotide polymorphism (SNPs) in the following genes were analyzed: Elastin (ELN); Titin (TTN); SRY-related HMG-box (SOX15); Insulin-like growth factor 2 (IGF2); Chemokine, CC motif, ligand 2 (CCL2); Collagen type 1 alpha 1(COL1A1); Collagen type 5 alpha 1 (COL5A1), and Tenascin C (TNC). There was evidence of a statistically significant association between the degree of injury and the IGF2 genotype (P = 0.034). In addition, there was evidence of a statistically significant association between the degree of muscle injury and CCL2 (P = 0.026) Finally, there was evidence of a statistically significant association between ELN and degree of injury (p = 0.009) and recovery time (P = 0.043). There was no evidence of a statistically significant association between any of the genes studied and degree of injury or recovery time for tendon injuries. SNPs in the IGF2, CCL2, and ELN genes may be associated to the degree and recovery time of NCMSTI.

#4 Measurement of pulmonary gas exchange variables and lactic anaerobic capacity during field testing in elite indoor football players
Authors: Angius L, Cominu M, Filippi M, Piredda C, Migliaccio GM, Pinna M, Milia R, Tocco F, Concu A, Crisafulli A.
Reference: J Sports Med Phys Fitness. 2013 Oct;53(5):461-9.
Summary: The aims of this study were: 1) to examine the gas exchange responses of elite indoor football players to a repeated sprint ability (RSA) test; and 2) to verify whether or not the excess of carbon dioxide production (CO2excess) correlates with blood lactate accumulation during RSA field testing. Eleven elite male indoor football players were recruited. A preliminary incremental exercise test on a treadmill was performed to elicit V'O2max. Then, participants underwent an RSA test consisting in a shuttle running through a course with various changes of direction while wearing a portable gas analyzer able to provide values of oxygen uptake, carbon dioxide production, and CO2excess. BLa concentrations during recovery were also measured. Results: The main results were that: 1) during the RSA test subjects did not reached the V'O2max level achieved in the preliminary test; 2) during the RSA test BLa levels were higher compared with the preliminary test; 3) the peak BLa concentration during recovery was significantly correlated with the average CO2excess.  It was concluded that the RSA test did not appear to be useful to elicit V'O2max. Rather, it seemed suitable to recruit subjects' lactic anaerobic capacity. Moreover, CO2excess appeared suitable for qualitatively estimate BLa accumulation during field testing.

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